Method of mounting a bearing to an air compressor, and air compressor having a bearing mounted by the method

ABSTRACT

A method of mounting a bearing to an air compressor including a shaft element having a first end defining a central cylindrical recess and a second is disclosed, which includes the steps of: fixing the second end of the shaft element to a center of a gear; inserting the first end of the shaft element through a central hole of a bearing to have an annular step of the shaft element abutted an inner ring of the bearing; and hitting the first end of the shaft element by a striking tool with a central pin to form an outwardly extending rim on the first end of the shaft element. With the method, the bearing can be firmly fixed between the outwardly extending rim and the annular step of the shaft element.

(a) TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of mounting a bearing to anair compressor, and an air compressor having a bearing mounted by themethod, wherein a striking tool is employed to hit one end of a shaftelement to form an outwardly extending rim on the end of the shaftelement, so that the bearing can be firmly connected with the shaftelement.

(b) DESCRIPTION OF THE PRIOR ART

FIGS. 10 and 11 show a conventional air compressor 1 for vehicles, whichbasically comprises a base frame 11, a cylinder 12 joined to the baseframe 11, a motor 13 mounted to the base 11, and a piston 14 fitted tothe cylinder 12. Through a gear mechanism 15 and a crank mechanism, themotor 13 can drive the piston 14 to conduct reciprocating motion withinthe cylinder 12. The reciprocating motion includes an intake stroke forallowing air to enter the cylinder 12 and a compression stroke forcompressing air in the cylinder 12 and forcing the compressed air out ofthe cylinder 12.

The gear mechanism 15 includes a first gear 151 (i.e., the drivinggear), which is mounted at an axle 131 of the motor 13, and a secondgear 152 (i.e., the driven gear) engaged with the first gear 151. Thecrank mechanism includes a counterweight 161 provided at the second gear152, a crankshaft 162, and a crankpin 164. One end of the crankshaft 162is fixed to a center of the second gear 152, and the other end of thecrankshaft 162 is fitted through a bearing 111 located in a mountinghole 110 of the base frame 11 and fixed by a screw 17 (with externalthreads 171) being screwed into a threaded hole 163 of the crankshaft162 (see FIGS. 9 and 10). In one embodiment, the other end of thecrankshaft 162 can be fitted through a metal bush 112 located in amounting hole 110 of the base frame 11, so that a snap ring 18 can beengaged with an annular groove 165 of the crankshaft 162 (see FIG. 8).The crankpin 164 is fixed to the counterweight 161 and the second gear152. The piston 14 is connected to the crankpin 164 such that the hole143 defined at the bottom end 142 of the rod portion 141 is fittedaround the crankpin 164. Since the crankpin 164 is at an offset from thecrankshaft 162, when the second gear 152 is rotated by the first gear151, the crankpin 164 can be driven to swing in a circle around thecrankshaft 162, which allows the piston 14 to conduct reciprocatingmotion within the cylinder 12.

FIG. 8 shows a conventional air compressor, one disadvantage of which isthat the snap ring 18 is easily loosened or detached from the crankshaft162 after the compressor has been used for a period of time. In anotherconventional air compressor, as shown in FIG. 9, due to insufficientdepth or strength of the threads engagement between the screw 17 and athreaded hole 163 of the crankshaft 162, the screw 17 is easily loosenedfrom the crankshaft 162. As a result, the metal bush 112 or the bearing111 cannot be properly connected with the crankshaft 162. Anotherproblem is that the main frame of an air compressor is usually made ofplastic, which can be slightly softened at a higher temperature. Thus,the mounting hole 110 is liable to undergo a greater force at some areaof the mounting hole 110 during the reciprocating motion of the piston14. As the piston 14 continues conducting reciprocating motion, themounting hole 110 can be gradually worn out. Thus, the rotational centerof the crankshaft 162 may not be fixed at a point. As can be seen inFIG. 12, wherein the motion path of the crankshaft 162 is schematicallyindicated by the symbol (A), while the motion path of the crankpin 164is schematically indicated by the symbol (C), which is non-circular.Under these circumstances, when the piston 14 conducts reciprocatingmotion within the cylinder 12, the motion path of the piston 14 maydeviate from its normal path, as shown by the dashed lines in FIG. 11,thus reducing the performance of the air compressor, and furthermore,the deviation of the motion path of the piston may cause damages on thehead portion 144 of the piston 14 and the bearing 111, thereby reducingthe service life of the air compressor.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a method of mounting abearing to an air compressor and, more particularly, to a smallcompressor, which includes a shaft element having a first end and asecond end. The method comprises the steps of: fixing the second end ofthe shaft element to a center of a gear; inserting the first end of theshaft element through a central hole of the bearing to have an annularstep of the shaft element abutted an inner ring of the bearing; andhitting the first end of the shaft element by a striking tool to form anoutwardly extending rim on the first end of the shaft element; wherebythe bearing can be firmly fixed between the outwardly extending rim andthe annular step of the shaft element.

Another object of the present invention is to provide an air compressor,which comprises a base frame, a cylinder with an air storage container,a gear, and a crank mechanism. The base frame defines a first mountinghole, which allows a pinion driven by a motor to pass, and a secondmounting hole for receiving therein a bearing including an outer ring,an inner ring, and a plurality of rolling balls disposed therebetween.The cylinder is fixed to or formed integrally with the base frame. Theair storage container is provided with one or more outlet tubes, andconnected and communicated with the cylinder. The gear is disposed inmesh with the pinion. The crank mechanism includes a counterweight, acrankpin connected with a piston, and a shaft element having a firstend, which defines a central cylindrical recess, and a second end,wherein the second end has a diameter greater than the first end, thusforming an annular step therebetween. The second end of the shaftelement is fixed to a center of the gear. The first end of the shaftelement is inserted through a central hole defined by the inner ring ofthe bearing and hitted by a striking tool with a central pin to form anoutwardly extending rim on the first end of the shaft element, so thatthe bearing can be firmly fixed between the outwardly extending rim andthe annular step of the shaft element.

Other objects, advantages, and novel features of the present inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a 3-dimensional view of a main structure of an aircompressor.

FIG. 2 shows a partially exploded view of the main structure of the aircompressor.

FIG. 3 shows a schematic working view of the present invention, whereina striking tool is employed to hit one end of a shaft element for fixinga bearing in place.

FIG. 4 shows a 3-dimensional view of the striking tool.

FIG. 5 shows a partial sectional view of the main structure of the aircompressor, wherein the striking tool is approaching the shaft elementto conduct a hitting operation.

FIG. 6 shows a partial sectional view of the main structure of the aircompressor, wherein the striking tool has completed the hittingoperation.

FIG. 7 shows a partial enlarged sectional view of a part circled in FIG.6.

FIG. 8 shows a partial exploded view of a main structure of a prior-artair compressor.

FIG. 9 shows a partial exploded view of a main structure of a secondprior-art air compressor.

FIG. 10 shows an exploded view of a third prior-art air compressor.

FIG. 11 shows a schematic plan view of the third prior-art aircompressor, wherein the motion path of the piston is indicated by dashedlines.

FIG. 12 shows a schematic view of the motion paths of the crankshaft andthe crankpin used in a prior-art air compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a main structure of a typical air compressor, throughwhich a method of mounting a bearing to an air compressor and, moreparticularly, to a small compressor, will be illustrated. As shown, theair compressor, indicated by reference numeral 2, generally includes abase frame 3, a cylinder 4 with an air storage container 41, a gear 51,and a crank mechanism including a counterweight (not shown), a crankpin53 connected with a piston (not shown), and a shaft element 52.

The base frame 3 defines a first mounting hole 31, which allows a pinion(not shown) driven by a motor (not shown) to pass, and a second mountinghole 32 for receiving therein a bearing 6 which has an outer ring 61, aninner ring 62, and a plurality of rolling balls 63 disposed therebetween(see FIG. 5).

The cylinder 4 is fixed to or formed integrally with the base frame 3.The air storage container 41 is provided with one or more outlet tubes411, 412, and connected and communicated with the cylinder 4. The outlettubes 411, 412 can be connected with a hose, a relief valve, or apressure gauge.

The gear 51 is disposed in mesh with the pinion (not shown). Thecounterweight (not shown) is provided on the gear 51. The shaft element52, which serves as a crankshaft for the air compressor 2, can be madeof a metal or alloy and has a first end and a second end opposite to thefirst end, wherein the second end has a diameter greater than the firstend, thus forming an annular step 521 therebetween, the first end of theshaft element 52 has a annular peripheral wall, which defines a centralcylindrical recess 524, and on which an annular surface 523 is formed.The shaft element 52 defines a cutout 522 at its second end so that thesecond end can be shaped as a non-circular portion, such as asemicircular portion. The gear 51 defines at its center a non-circularhole, such as a semicircular hole, corresponding to the non-circularportion formed at the second end of the shaft element 52.

The method of the present invention comprises the following steps:

Step 1: fixing the second end of the shaft element 52 to a center of thegear 51; for example, the second end of the shaft element 52 beingsnugly fitted into the corresponding hole defined at the center of thegear 51;

Step 2: inserting the first end of the shaft element 52 through thecentral hole of the bearing 6 to have the annular step 521 of the shaftelement 52 abutted the inner ring 62 of the bearing 6 (see FIG. 5); and

Step 3: hitting the first end of the shaft element 52 by a striking tool7 to form an outwardly extending rim 525 on the first end of the shaftelement 52 (see FIG. 6); as a result, the bearing 6 can be firmly fixedbetween the outwardly extending rim 525 and the annular step 521 of theshaft element 52.

To facilitate forming an outwardly extending rim 525 on the first end ofthe shaft element 52, it is preferred that, as shown in FIG. 4, thestriking tool 7 includes a shank having a press head 71 at one end,which is provided with a central pin 75 having a diameter (A) slightlygreater than the diameter (B) of the central cylindrical recess 524 (seeFIG. 5) and defining a depression around the central pin 71. An annularsurface 72, which has a level lower than the central pin 75, is formedaround the depression. More specifically, the depression is delimited bya concave surface 73 at a bottom of the central pin 75, and a conicalsurface 74 formed between the concave surface 73 and the annular surface72. In a hitting operation, the central pin 75 can be inserted into thecentral recess 524 of the shaft element 52 to applied radial force (F)to the annular peripheral wall of the shaft element 52 (see FIG. 7) tofacilitate deformation of the top of the cylindrical wall. With thetool, the outwardly extending rim 525 can be formed into a specificshape, as shown in FIG. 7, wherein the outwardly extending rim 525 is aportion of the shaft element 52 bounded by a first annular taperedsurface 523′, which is formed by the conical surface 74 of the strikingtool 7 urging against the annular surface 523 of the shaft element 52,an annular convex surface 527, which is formed by the concave surface 73of the striking tool 7 urging against an inner surface of the centralcylindrical recess 524 of the shaft element 52 close to the annularsurface 523, and a second annular tapered surface 526, which is forcedby the central pin 75 to contact the inner ring 62 of the bearing 6.

By using the method of the present invention, the bearing 6 can befirmly mounted with the shaft element 52 in the second mounting hole 32to prevent possible damages, and the reciprocating motion of the piston14 can follow its normal straight path. An air compressor, in which thebearing associated with the crankshaft is mounted according to themethod of the present invention, the piston can conduct reciprocatingmotion more smoothly, and thus the performance and service life of theair compressor can be increased.

As a summary, the present invention provides a method of mounting abearing to an air compressor, and an air compressor, in which a bearingis mounted by using the method. By using a striking tool hitting one endof a shaft element, the bearing can be firmly fixed between an outwardlyextending rim and an annular step of the shaft element.

While the invention has been described with reference to the preferredembodiments above, it should be recognized that the preferredembodiments are given for the purpose of illustration only and are notintended to limit the scope of the present invention and that variousmodifications and changes, which will be apparent to those skilled inthe relevant art, may be made without departing from the scope of theinvention.

I claim:
 1. A method of mounting a bearing to an air compressor whichincludes: a base frame defining a first mounting hole, which allows apinion driven by a motor to pass, and a second mounting hole forreceiving therein a bearing which has an outer ring, an inner ringdefining a central hole, and a plurality of rolling balls disposedbetween the outer ring and the inner ring; a cylinder fixed to or formedintegrally with the base frame; an air storage container provided withone or more outlet tubes and connected with the cylinder; a gear in meshwith the pinion; and a crank mechanism including a counterweightprovided on the gear, and a shaft element having a first end and asecond end, wherein the second end has a diameter greater than the firstend, thus forming an annular step therebetween, the first end of theshaft element having an annular peripheral wall, which defines a centralcylindrical recess, and on which an annular surface is formed the methodcomprising the steps of: fixing the second end of the shaft element to acenter of the gear; inserting the first end of the shaft element throughthe central hole of the bearing to have the annular step of the shaftelement abutted the inner ring of the bearing; and hitting the first endof the shaft element by a striking tool to form an outwardly extendingrim on the first end of the shaft element; whereby the bearing is firmlyfixed between the outwardly extending rim and the annular step of theshaft element.
 2. The method of claim 1, wherein the striking toolincludes a shank having a press head that is provided with a central pinhas a diameter slightly greater than the central cylindrical recess anddefines a depression around the central pin, an annular surface beingformed around the depression and having a level lower than the centralpin, the depression delimited by a concave surface at a bottom of thecentral pin, and a conical surface formed between the concave surfaceand the annular surface.
 3. The method of claim 2, wherein the outwardlyextending rim is a portion of the shaft element bounded by a firstannular tapered surface, which is formed by the conical surface of thestriking tool urging against the annular surface of the shaft element,an annular convex surface, which is formed by the concave surface of thestriking tool urging against an inner surface of the central cylindricalrecess of the shaft element, and a second annular tapered surface, whichis forced by the central pin of the striking tool to contact the innerring of the bearing.
 4. An air compressor, comprising: a base framedefining a first mounting hole, which allows a pinion driven by a motorto pass, and a second mounting hole for receiving therein a bearingwhich includes an outer ring, an inner ring defining a central hole, anda plurality of rolling balls disposed therebetween; a cylinder fixed toor formed integrally with the base frame; an air storage containerprovided with one or more outlet tubes, and connected and communicatedwith the cylinder; a gear in mesh with the pinion; and a crank mechanismincluding a counterweight provided on the gear, a crankpin connectedwith a piston, and a shaft element having a first end, which defines acentral cylindrical recess, and a second end, wherein the second end hasa diameter greater than the first end, thus forming an annular steptherebetween, the second end of the shaft element being fixed to acenter of the gear, the first end of the shaft element being insertedthrough the central hole of the inner ring of the bearing and beinghitted by a striking tool to form an outwardly extending rim on thefirst end of the shaft element, so that the bearing is firmly fixedbetween the outwardly extending rim and the annular step of the shaftelement.
 5. The air compressor of claim 4, wherein a cutout is definedat the second end of the shaft element to form a non-circular portion tobe engaged with a non-circular hole defined at the center of the gear.6. The air compressor of claim 4, wherein the outwardly extending rim isa portion bounded by a first annular tapered surface, an annular convexsurface, and a second annular tapered surface.